This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Evaluate safety and efficacy of PN401 in reduction of seizures and infections, improvement of speech and language and cognitive functions in patients with pyrimidine responsive syndrome of neurological dysfunction and susceptibility to infection, evaluate quality of life, and describe effects of PN401 on signs and symptoms of the syndrome.